Don’t use PayPal. Usually a conference involves more money than usual. Another problem is that conferences are a big risk, people don’t like speakers, too crowded, the sound or wifi is awful, the venue cancels at last minute and the alternative sucks, ... So there are too much chargebacks and PayPal usually frizzes the money until the chargeback period clears. (You can agree with them, you can disagree with them, but you can’t ignore that they have this informal “rule”.)
Some examples: https://www.hnsearch.com/search#request/submissions&q=paypal...
